Diagnostic, curative or therapeutic agents are administered to the eye in small quantities during ophthalmic examinations and treatments. It is often convenient to administer more than one agent at a time, such as a dye and an anesthetic, so that the eye is prepared simultaneously for multiple tests. Eye droppers and solid applicators are commonly used to administer these agents, but each has its own disadvantages.
Eye droppers are squeeze bottles that exude one drop of solution at a time, and provide multiple doses of a given agent in a single bottle. Although they are convenient, the pharmacological solutions used in the eyedroppers have disadvantages. The solutions are unstable over time and therefore have a limited shelf life. Temperature fluctuations can cause precipitation of various compounds, so less ophthalmic agent is administered to a patient than would be expected in a full solution, or an irritating solid aggregate may be dispensed into a patient's eye. Precipitation can also occur if an eye dropper bottle is not closed tightly thereby causing evaporative loss of water. After the bottles of solution are opened, the solutions may be contaminated by microbes. Over time, this microbial contamination grows and degrades the agents in solution, reducing their benefit for patients and adding the risk of infection. To deal with this problem and to increase the shelf life to a commercially-viable period of time, various preservatives are added to ophthalmic solutions to prevent microbial growth. Unfortunately, many patients are allergic to these preservatives, and the preservatives are therefore irritating to the patient's eye. Single-use vials of solution are available preservative-free, but these vials are inconvenient to use and expensive. It is desirable to provide a cost-effective, convenient dispenser of controlled quantities of ophthalmic agents that remains sterile until use, and has no preservatives.
Eyedroppers have other disadvantages. The volume of fluid dispensed by an eyedropper is often more than an eye can hold, and therefore the excess fluid leaks out. When it does, it is impossible to determine the amount of medicament administered to the eye. In addition, the liquid that leaks out of the eye can stain a patient's clothing, such as the case when fluorescein sodium, a dye commonly used in ophthalmic diagnoses, is used. Also, an eye dropper is not satisfactory when very small quantities of medications are needed, for example the quantities less than that present in one drop of a standard ophthalmic eyedropper formulation. It is desirable to administer ophthalmic agents in a way that delivers a known small quantity that remains in the patient's eye.
The prior art is replete with single-use applicators made of filter paper, plastic rods, polymer film or other dry substrate materials that are physically touched to the eye or adnexa. A solution of the agent of choice, such as fluourescein sodium, is applied to the substrate and allowed to dry. The dry, impregnated applicators are applied directly to the patient's eye, and the pharmacological agent dissolves in the patient's tears. These devices suffer serious disadvantages. First, application of a dry surface to the eye is very irritating. Second, dissolution into the tears of the eye is slow because of the extremely small volume of fluid present initially. The problem is exacerbated if the patient is suffering from dry eye syndrome, a common presenting complaint in ophthalmology. Plus, waiting for dissolution of the ophthalmic agent is a lengthy process, prolonging the irritation and discomfort for the patient. It is desirable to provide a method that delivers the agents quickly and with an applicator that is minimally irritating to the eye.
It is common practice to administer diagnostic dyes with small strips of filter paper that have been soaked in the dye and dried. To simultaneously deliver more than one agent at a time, a practitioner may add a drop of anesthetic to one end of the strip, dissolving the dye, and then touch the adnexa of the eye with the wetted filter paper. This, too, however, has its disadvantages. The filter paper is insufficiently rigid to hold the drop, and the excess fluid drops off the end of the strip. As a result, less anesthetic is given to the patient than what is in one drop, but the actual quantity is unknown, and additional anesthetic often must be administered by eyedroppers. Furthermore, upon wetting, many of the strips droop, complicating their handling. Often the dye strips are manufactured with much more dye than what is really needed for the diagnostic procedure, leading to waste, extra expense and possible damage to the patient's clothing. Practitioners in such cases wipe off the excess dye, which further illustrates the sub-optimal state of the art. Again, it is desirable to administer ophthalmic agents in a way that delivers a known quantity that remains in the patient's eye.
Additional problems arise when delivering multiple agents to the eye simultaneously. For example, it is common practice to administer a dye and an anesthetic combination during the procedure of measuring intraocular pressure using applanation or other forms of tonometry. When combined in a solution for application by eyedropper, however, many dyes and anesthetics, such as fluorescein sodium and proparacaine, form precipitates and fall out of solution or otherwise adversely affect the solubility of the companion agents. Interestingly, the same is true for the preparation of ophthalmic strips: many common ophthalmic agents form precipitates as they dry on the strip or otherwise adversely affect the solubility of the other agents, thereby rendering them useless. This means that heretofore eyedroppers and strip applicators have not been optimal delivery devices for delivering multiple agents to the eye.
Therefore, it is an object of this invention to provide an apparatus that simultaneously delivers a known quantity of one or more ophthalmic agents to the eye in a single application, with little or no waste. It is another object of this invention to provide an apparatus that delivers multiple ophthalmic agents in a disposable, sterile, single-use applicator for immediate use. It is a further object to provide an applicator having extended shelf-life with no preservatives. It is a further object of this invention to deliver ophthalmic agents in a minimally irritating way.